Changes in the Content of Chlorophyll and Redox Components of the Thylakoid Membrane during Development and Senescence of Beech (Fagus sylvatica) Leaves

Leaves from 145-year-old and 44-year-old beech trees were harvested during 1991-1993. Chlorophyll (Chi) and redox components of the thylakoid membrane, including P-700, cytochrome / (C yt/) and D, protein, were determined with the following results. Chi a + b, P-700 and C y t/p er unit of fresh weight (FW), dry weight (DW ) and leaf area (LA ) increase significantly during leaf development. This can be attributed to a massive membrane syn­ thesis and new thylakoid formation in the cells. The Chi a/Chl b ratio decreases with the synthesis of Chi during the development of beech leaves and is reduced further with Chi breakdown in the stage of senescence. When expressed on the basis of Chi, a reduction in the amount of P-700 and C y t / is observed during the growth stage, indicating a marked enlargement of the functional photosynthetic unit. During senescence of beech leaves, Chi breaks down, and P-700 and C y t/p e r unit of FW, DW and LA decrease dramatically with the decline in Chi levels. However, when expressed on the basis of Chi, P-700 remains rela­ tively constant, while C y t/sh o w s a pronounced increase. The uncommon pattern of Cyt / change in senescent beech leaves and the relationship between the amount of Chi and the content of C yt/throughout an entire growth period of beech leaves are discussed.